src/bin/random-pick-index.rs

Author: bestgopher

src/bin/random-pick-index.rs

@@ -0,0 +1,42 @@
+fn main() {}
+
+/**
+ * Your Solution object will be instantiated and called as such:
+ * let obj = Solution::new(nums);
+ * let ret_1: i32 = obj.pick(target);
+ */
+struct Solution {
+    index_map: std::collections::HashMap<i32, Vec<usize>>
+}
+
+
+/**
+ * `&self` means the method takes an immutable reference.
+ * If you need a mutable reference, change it to `&mut self` instead.
+ */
+impl Solution {
+    fn new(nums: Vec<i32>) -> Self {
+        let mut index_map = std::collections::HashMap::new();
+
+        nums
+            .into_iter()
+            .enumerate()
+            .for_each(|(index, value)| {
+                index_map.entry(value)
+                    .and_modify(|y: &mut Vec<usize>| y.push(index)).or_insert(vec![index]);
+            });
+
+        Self { index_map }
+    }
+
+    fn pick(&self, target: i32) -> i32 {
+        use rand::Rng;
+
+        match self.index_map.get(&target) {
+            Some(x) => {
+                x[rand::thread_rng().gen_range(0..x.len())] as i32
+            }
+            None => 0
+        }
+    }
+}